Left ventricular ECG changes

Hemodynamic background of ECG changes

Pathologies causing left ventricular (LV) overload are inevitably reflected on the electrocardiogram. The classic model of such overload is mitral regurgitation (MR). To maintain adequate systemic blood flow, the heart compensatorily increases the total stroke volume and ejection fraction (EF).

In acute onset of the valvular defect—for example, due to infective endocarditis or rupture of the chordae tendineae (papillary muscles)—sudden volume overload of the non-compliant left atrium occurs. This leads to a rapid pressure rise and pulmonary edema. Chronic regurgitation (against the background of ischemic or non-ischemic cardiomyopathy, rheumatic disease) triggers another mechanism. The atrium and ventricle gradually dilate, acting as a reservoir for excess blood volume. Over time, the effective forward stroke volume drops, heart failure develops, and prolonged overload forms hypertrophy—the main substrate for pathological patterns on the ECG.

Characteristic ECG pattern

Myocardial structural remodeling manifests as a complex of electrophysiological shifts. The following typical findings can be recorded on the ECG:

• Intraventricular conduction disturbances: incomplete left bundle branch block is frequently registered (QRS complex duration reaches 0.11 s).
• Nonspecific repolarization changes: in the left precordial (V5–V6) and standard (I, aVL) leads, ST-segment depression (up to 1.0 mm) and T-wave flattening are observed. It is important to remember that these signs are secondary to hypertrophy and conduction disturbances; they do not indicate acute ischemia or injury.
• Rhythm changes: left atrial dilation becomes the structural substrate for permanent atrial fibrillation. Initially, a tachy-systolic variant (HR 100–142 bpm) may be recorded, which transitions to normosystolic under therapy (about 76 bpm) while maintaining a normal QT interval.

Mitral valve prolapse (leaflet protrusion by more than 2 mm into the atrial cavity) stands out separately; it may be accompanied by chest pain and specific ECG changes that can mistakenly mimic ischemic heart disease.

Structural substrate according to echocardiography

ECG signs of hypertrophy and overload find direct confirmation on echocardiography. Characteristic parameters of concentric LV hypertrophy are:

• Interventricular septum thickness up to 1.4 cm and posterior wall up to 1.3 cm (with a normal limit of no more than 1.1 cm).
• Increased myocardial mass index (e.g., 128 g/m² with a norm up to 115 g/m² for men) and relative wall thickness index (0.48).
• Preserved end-diastolic dimension (EDD about 5.4 cm) without marked dilation of the ventricle itself.

Against the background of such hypertrophy, diastolic function naturally suffers. Type 2 dysfunction develops (pseudonormal filling type): the E/e' ratio increases (>9), the E/A ratio reaches 1.2, and the E-wave deceleration time is prolonged to 160 ms. At the same time, global contractility may remain preserved (Simpson EF 55%).

Radiological correlations

Chest X-ray complements the diagnostic picture. In decompensated or chronic pathology, the cardiac silhouette enlarges to the left (cardiothoracic ratio exceeds 0.5), and the cardiac configuration acquires an aortic shape with a dense, unfolded aortic arch.

Isolated left atrial enlargement may manifest as enlargement of its appendage, subcardial shadow, and characteristic upward displacement of the left main bronchus. At the same time, acute severe mitral regurgitation can cause alveolar pulmonary edema with practically normal heart size and shape.

Comprehensive assessment and exclusion of comorbid conditions

To confirm that the ECG changes are specifically related to isolated left heart overload, a comprehensive examination is performed. Clinically, hemodynamic impairments are confirmed by decreased exercise tolerance (e.g., 340 m in the 6-minute walk test, corresponding to NYHA functional class II).

The absence of local contractility disturbance zones excludes prior myocardial infarction. Negative results of brachiocephalic artery duplex scanning (IMT 0.8 mm, no plaques) and a normal funduscopy picture (absence of Salus–Gunn sign) rule out systemic target organ damage. Normal spirometry values (FEV₁ 88%, FEV₁/FVC ratio 0.78) and intact renal arteries exclude pulmonary and renovascular causes of dyspnea, confirming that heart failure with preserved ejection fraction (HFpEF) underlies the clinical picture.

Class and exam questions

What else to study on this topic

• Pathogenesis and diagnosis of acute mitral regurgitation
• Mitral valve prolapse syndrome: etiology and imaging
• Echocardiographic criteria for LV diastolic dysfunction
• Criteria for heart failure with preserved ejection fraction (HFpEF)
• Causes of flail mitral valve leaflet formation

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.